1. Field of the Invention
The present invention relates to a magnetic recorder/reproducer. More specifically, it relates to a magnetic recorder/reproducer having rotary heads for slantingly or vertically scanning the same by the rotary heads thereby recording digital signals in a magnetic tape and reproducing the same, and particularly to an improvement in interleaving of the data thereof.
2. Description of the Prior Art
Heretofore well known in the art is a rotary head-type PCM magnetic recorder/reproducer which converts audio signals into digital signals for recording the digital signals in a magnetic tape and reproducing the recorded digital signals. In general, a rotary head-type PCM magnetic recorder/reproducer employs error correction codes for correcting errors caused in the data upon recording/reproducing of the magnetic tape.
The error correction codes are adapted to correct the errors caused in the data following recording/reproducing of the magnetic tape thereby to reproduce high definition audio signals. However, when the number of the errors is beyond the correction ability to disable the error correction, compensation must be performed by means such as interpolation by taking the mean value of adjacent data. Further, most of the errors caused on the magnetic tapes are burst errors, and hence the erroneous data are dispersed by interleaving processing for improving the ability of the error correction codes.
As hereinabove described, compensation processing is performed when the errors cannot be corrected, and mean value interpolation is employed as an effective compensation process with simple circuit structure. Such mean value interpolation is performed on condition that the adjacent data are correct.
Therefore, data of odd sample groups are separated as far as possible from those of even sample groups when the interleaving operation is performed.
FIGS. 1 and 2 show magnetization patterns recorded on a magnetic tape by a conventional rotary head-type PCM magnetic recorder/reproducer.
The following description is made of a rotary head-type PCM magnetic recorder/reproducer of a two-head helical scanning system, which is taken as a typical example.
In FIGS. 1 and 2, a magnetic tape T travels in the direction indicated by an arrow D and is scanned by rotary heads in the direction indicated by an arrow S. The data recorded in the magnetic tape T are of two channels A and B, and distributed into even sample groups a and odd sample groups b. For example, symbol a with symbol A+B indicates even sample groups of the channels A and B, and symbol Aa indicates an even sample group of the channel A.
The volume of interleaving is generally determined in consideration of burst length of errors and correction ability of error correction codes, and an even sample group a and an odd sample group b may be in line over a scanning interval as shown in FIG. 1 or to the contrary.
FIG. 2 shows the even sample groups a and the odd sample groups b arrayed in equally divided scanning intervals. In the interleaving operation performed in this manner, errors are caused in continuous data when one of the rotary heads is instantaneously silted by magnetic powder coming off from the magnetic tape T, i.e., when the reproduced signals from one of the rotary heads are interrupted. Thus, it has been impossible to perform the mean value interpolation, which causes harsh noise.